<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <p id="p-test">123123</p>
    <p>456</p>
    <p>789</p>
    <button onclick="alert('123')">这是个按钮</button>
    <input type="text" onblur="validateInput()">
    <button onclick="validateInput()">校验输入框</button>
</body>
<script src="./demo.js"></script>
</html>